API BackgroundUnchangedfrom2012LARThe Antecedent Precipitation Index (API) method is currentlyusedbyTVARiverOperationsinforecastingUnchanged from 2012 LAR currently used by TVA River Operations in forecasting and was used by TVA in previous analyses of the TennesseeRiversystemfortheTVANuclearPower Tennessee River system for the TVA Nuclear Power Group.The API method is currentl y used b y TVA River yyOperations to accomplish their federally mandated, integrated operation of the TVA reservoir system which includes flood control responsibilitiesIn CDQ000020080052, the API method was ddddhd 14 compare d to two in d ustry stan d ar d met h o d s.

Computed API Prior to Main Storm 12The API for any day is equal to that of the previous day multiplied by 0.9, plus

Unsteady Flow Rules*Water surface elevations at appropriate headwater/tailwatersectionsareextractedatthe headwater/tailwater sections are extracted at the beginning of each computational time stepItlbdflthtti

event Correction for submergence was performed for each eventDam ModificationsNot included HESCO Concertainers IncludedOperationalAllowancesNot includedEvaluatedfor each simulationEvaluatedfor each simulation 34Rim Leaks at Fort Loudoun, Watts Bar, and

operability Not consideredIf operating deck was overtopped then the gates are assumed to

be inoperable on the If operating deck was overtopped then the gates are assumed to be inoperable on the recession siderecession sideDownstream Dams No failures assumedNo failures assumedNo failures assumed Loss Method A PI A PI A PI 35Norris Subbasins411Melton Hill Subbasins1011 Hydrologic Calculation Flow Chart 36